If $x \bigtriangleup y = xy+4x-y$ and $x \veebar y = 3x-6$, find $5 \veebar (-5 \bigtriangleup 6)$.
Explanation: We don't need to find $-5 \bigtriangleup 6$ because $x \veebar y$ depends only on the left operand. Find $5 \veebar y$ $ 5 \veebar y = (3)(5)-6$ $ \hphantom{5 \veebar y} = 9$.